Alterations in the cell surface are implicated in the changes in cell properties which accompany oncogenic transformation. An understanding of the changes in the surface membrane of mouse mammary carcinomas forms the broad basis of this proposal. The surface membrane composition of cultured mammary tumor cells of varying etiology, i.e., chemical carcinogen, virus, hormone, and varying tumorigenicity, as well as cells derived from normal mammary gland, will be determined. Surface proteins, glycolipids, aminoacyl fucosides, phospholipids, fatty acids, and cholesterol will be analyzed. Studies of the arrangement of these components in the surface membrane will involve use of reagents which are limited to reaction with external, accessible components such as galactose oxidase-tritiated sodium borohydrid treatment and trinitrobenzene sulfonic acid. The surface membrane organization will also be studies by fluorescence spectroscopy to measure microviscosity. The pertinent membrane aspects determined with the culture cells will then be examined in mammary carcinomas, preneoplastic mammary lesions, and normal mammary gland. These combined studies should define surface membrane alterations related to transplantability of epithelial mammary gland cells and explored the basis for these alterations.